The role of calcium as the stimulus-secretion coupling agent has been firmly established. However, precise knowledge obtained from a number of different aspects is needed in order to define in chemically- precise terms the nature of calcium's role. The major thrust of this project is to elucidate the fundamental mechanism whereby calcium regulates the secretory process. An understanding of the role of calcium necessitates consideration of other potential mediators of secretion, including cyclic AMP and prostaglandins. The proposed work involves a study of the effect of ACTH on levels of cyclic AMP, cyclic GMP and prostaglandins in the adrenal cortex and the influence of calcium on these levels. These investigations will be carried out on intact perfused cat adrenal glands and on isolated cortical cell supensions prepared by trypsin digestion.